Use @require and other decorators to simplify code imports/checking
Return matrix instead of array for laplacian functions
Whitespace cleanup and formatting
Refector conditional so there is only one return
add weight to astar_path_length's call to astar_path
Merge pull request #871 from tdihp/patch-1

add weight to astar_path_length's call to astar_path
Bug writing shapes in GEXF format
Merge pull request #875 from hagberg/gexf-shape

Bug writing shapes in GEXF format
Fix katz centrality doctest formatting
Fix core tests

Adjust test graph to map nodes since the new havel hakimi algorithm generates different node ordering
Merge pull request #876 from hagberg/core-tests

Fix core tests
Merge pull request #877 from hagberg/katz-test

Fix katz centrality doctest formatting
Merge pull request #833 from hagberg/laplaican-matrix

Laplaican matrix functions should return matrix
Fix import error and typos in scc tests
Remove failing threshold graph test

Need to rework for matrix type return from laplacian_matrix
Merge pull request #882 from hagberg/threshold-test

Threshold test
single_source_dijkstra_path passes cutoff
Merge pull request #883 from tdihp/patch-2

single_source_dijkstra_path passes cutoff
Create nonrecursive function for simple_cycles

Copied simple_cycles to recursive_simple_cycles and added a new
simple_cycles that is the same algorithm but not recursive.  Two
changes in the API for simple_cycle are that
1) it now returns a generator instead of returning a list.
2) Cycles no longer repeat the first node as the last.  The last
node in the list is assumed to connect to the first node on the list.

Tests added to compare output of simple_cycles and recursive_simple_cycles

Thanks to erikasantos and friedsoap for instigating this and suggesting
helpful changes (which I incorporated).  This addresses #874 #888 #889
Fix documentation typos for clustering